Wax appearance temperatures of vegetable oils determined by differential scanning calorimetry: effect of triacylglycerol structure and its modification

Crystallization and wax appearance temperatures of a series of vegetable oils (natural, genetically and chemically modified) were studied using differential scanning calorimetry (DSC). The fatty acid chains of a triacylglycerol molecule have a bend ‘tuning fork’ conformation and undergo molecular stacking during the cooling process. Wax crystallization at low temperature is controlled by steric and geometrical constrains in these molecules. This study describes an approach to quantify and predict wax appearance temperature of vegetable oils based on the statistical analysis of DSC and NMR data. A molecular modeling program was used to design triacylglycerol molecules with different fatty acid (e.g. oleic and linoleic) chains to illustrate their effect on the crystallization process. Effect of pour point depressant (PPD) additives on vegetable oil crystallization is also discussed.